The present invention relates in general to antifouling coatings. More specifically, the present invention relates to a tailorable surface topology for antifouling coatings.
The accumulation of microorganisms on wetted surfaces, or biofouling, is a ubiquitous problem for materials in a broad range of applications, such as medical devices, marine instruments, food processing, and even domestic drains. Generally, bacteria initiate biofouling by forming biofilms, which include highly ordered adherent colonies, commonly within a self-produced matrix of extracellular polymeric substance.
In the medical field, infection is a potential complication of implanted medical devices. Bacterial colonization and subsequent biofilm formation are difficult to diagnose and treat. Biofilms are a primary cause of persistent infections because of their resistance to antibiotics, potential release of harmful toxins, and ability to spread microorganisms. Biofilms can also cause implantable devices to malfunction.
Often, extreme measures, such as removal of the infected device from the patient's body, are the only viable management option. Although disinfection techniques and prophylactic antibiotic treatment are used to prevent colonization during procedures, such practices are not completely effective in preventing perioperative bacterial colonization. Moreover, the risk of bacterial colonization on, for example, a prosthetic joint can be present even long after it has been implanted. The use of implantable devices, such as prosthetic joints, heart valves, artificial hearts, vascular stents and grafts, cardiac pacemakers and defibrillators, nerve stimulation devices, gastric pacers, vascular catheters and ports (e.g., Port-A-Cath)) is growing, and therefore, the number of immunocompromised patients resulting from advanced therapeutics is also growing.
For a variety of reasons, antibiotic treatments to eliminate colonization and infection associated with implantable substances and devices can be limited in their ability to eradicate bacteria and fungi involved in the above processes. For example, antibiotic concentrations can be reduced deep inside the biofilm due to limited diffusion. Antibiotics also may be unable to generally eliminate “the last” pathogen cells, which is typically accomplished by the immune system that also may not optimally function in the presence of implantable devices. Microorganisms also possess the ability to persist, i.e., to become metabolically inactive and thus functionally relatively resistant to antibiotics. The pandemic of antibiotic resistance makes treating device-associated infections even more challenging. In fact, antibiotic resistance is frequently encountered with microorganisms that cause device-associated infections (e.g., Enterococci and Staphylococci). Therefore, there is a clear need for means and methods to prevent the formation of biofilms on implantable devices.
Consequently, considerable efforts were dedicated, in recent years, to developing antibacterial surfaces. Such surfaces can be classified into two categories: (i) antifouling surfaces that prevent the adhesion of microorganisms, and (ii) bactericidal surfaces that trigger bacteria killing.
Typical strategies for the design of antibacterial surfaces involve either supramolecular (non-covalent) coating of the surface or modification of the surface (i.e., chemical modification or structuring). Antifouling properties are commonly obtained by the incorporation of, for example, oligo or poly(ethylene glycol) (PEG) to increase hydrophilicity and resist bacteria attachment. Bactericidal characteristics, on the other hand, may be obtained by functionalization with releasable bacteria-killing substances, such as silver nanoparticles (Ag NPs) and antibiotics, or decoration with contact-killing bactericidal moieties like quaternary ammonium salts. Current technologies, however, suffer several shortcomings including, just to name a few, long-term antibacterial performances and stability, development of bacterial resistance, and scalability to an industrial setting. While bacterial cell lysis on biocide-functionalized surfaces reduces the rate of biofilm formation, recent reports evidenced that a combination of both antifouling and bactericidal properties was necessary to insure long-term efficacy of the surfaces.
An environmentally friendly and easy to process method for protecting surfaces and devices for prolonged periods of time using an antimicrobial/antifouling strategy to prevent biofilm formation remains a technologic and scientific challenge.